Abstract

Electrical stimulation of certain hypothalamic regions in cats and rodents can elicit attack behaviour, but the exact
location of relevant cells within these regions, their requirement for naturally occurring aggression and their
relationship to mating circuits have not been clear. Genetic methods for neural circuit manipulation in mice provide a
potentially powerful approach to this problem, but brain-stimulation-evoked aggression has never been demonstrated
in this species. Here we show that optogenetic, but not electrical, stimulation of neurons in the ventromedial
hypothalamus, ventrolateral subdivision (VMHvl) causes male mice to attack both females and inanimate objects, as
well as males. Pharmacogenetic silencing of VMHvl reversibly inhibits inter-male aggression. Immediate early gene
analysis and single unit recordings from VMHvl during social interactions reveal overlapping but distinct neuronal
subpopulations involved in fighting and mating. Neurons activated during attack are inhibited during mating,
suggesting a potential neural substrate for competition between these opponent social behaviours.